The inorganic/organic hybrid membranes modified by MMA were deposited on the porous alpha -Al2O3 substrates (pore size, 2 mum) by the sol-gel technology. It was found that the introduction of MMA can not only improve the membrane formation properties, but also increase the selectivity of O-2/N-2 and O-2/CO2. On the other hand, the modified hybrid membranes have more dense structure.